Apparatus for stirring and transporting slurries

ABSTRACT

Apparatus for stirring and transporting slurries in vessels of great volume used, for example, in the alumina industry. The apparatus of the invention is adapted to replace, with greater economic efficiency, the generally previously-used pneumatic system for the stirring and transportation of slurries. The present apparatus uses a tube centrally placed in the vessel; a turbine pump driven, for example, by an electric motor, is mounted in the tube. The turbine pump raises the slurry to the level of some apertures or windows in the tube. The thus-raised slurry overflows through the windows to fall partly into the same vessel and partly into a conduit for transportation out of such vessel. The conduit has windows through which the level of the slurry is maintained constant in the vessel. The device provides an intensive stirring and the transportation of the slurry independent of the volume of the vessel and independent of the density of the slurry, with a much lower power consumption as compared to pneumatic stirring. Such intensive stirring eliminates the encrustation on the bottom of the vessels and on the side walls of the receiver. The system of the invention also ensures the perfect vertical homogenization of the slurry, eliminating at the same time foaming and the eventual chemical reactions between the components of the slurry and those of air, and the consequent breaking down of the solid phase of the slurry.

United States Patent [1 1 Stefanoiu APPARATUS FOR STIRRING AND TRANSPORTING SLURRIES [75] Inventor: Constantin C. Stefanoiu, Oradea,

Romania 73] Assignee: Uzina De 'Alumina Oradea, Soseauau Borsului Kn., Romania 22 Filed: Oct.26, 1971 211 App]. No.: 192,629

[30] Foreign Application Priority Data Primary Examiner-William I. Price Assistant Examiner-Alan I. Cantor Attorney-Arthur O. Klein [5 7] ABSTRACT Apparatus for stirring and transporting slurries in ves- 11 3,741,530 June 26, 1973 sels of great volume used, for example, in the alumina industry. The apparatus of the invention is adapted to replace, with greater economic efficiency, the generally previously-used pneumatic system for the stirring and transportation of slurries. The present apparatus uses a tube centrally placed in the vessel; a turbine pump driven, for example, by an electric motor, is mounted in the tube. The turbine pump raises the slurry to the level of some apertures or windows in the tube. The thus-raised slurry overflows through the windows to fall partly into the same vessel and partly into a conduit for transportation out of such vessel. The conduit has windows through which the level of the slurry is maintained constant in the vessel. The device provides an intensive stirring and the transportation of the slurry independent of the volume of the vessel and independent of the density of the slurry, with a much lower power consumption as compared to pneumatic stirring. Such intensive stirring eliminates the encrustation on the bottom of the vessels and on the side walls of the receiver. The system of the invention also ensures the perfect vertical homogenization of the slurry, eliminating at the same time foaming and the eventual chemical reactions between the components of the slurry and those of air, and the consequent breaking down of the solid phase of the slurry.

6 Claims, 3 Drawing Figures Pmmtnmzs Ian 3.141. 530

SHEEI 1 If 2 APPARATUS FOR STIRRING AND TRANSPORTING SLURRIES This invention relates to an apparatus for the stirring and transportation of slurries in vessels of great volume, such as those used in the crystallization operation during the preparation of aluminum oxide.

There are previously known devices for the stirring and transportation of slurries which include a tube centrally placed in the vessel, such tube forming a part of a large pump in which there is disposed a driven paddle shaft carrying a helical paddle which forces the slurry downwardly into the lower part of the vessel through the central tube, the slurry then rising in the vessel outwardly of the tube. When such known devices are used, the transportation of the slurry from one vessel into another is carried out through fall or free-flow by reason of differences in height. I

These known devices have the disadvantage that, because the helical paddle or impeller is disposed near the surface of the slurry, air is readily absorbed or taken in through the top of the central tube. Thisleads to the formation of an air column beneath the impeller, thereby reducing the efficiency of the equipment. Also, in these devices, once the solid phase has settled down on the bottom of the vessel, it cannot again be incorporated in the slurry; the resulting sediments form deleterious crusts on the inner surface of the vessel.

The apparatus of the present invention for the stirring and transportation of slurries overcomes the above disadvantages of the described prior art devices.

7 Briefly, in accordance with an illustrative embodiment of the invention, there is employed a centrally disposed tube in which there is mounted a turbine pump driven by a motor. The pump raises the slurry in the tube from the lower part of the vessel, and discharges it through some windows or apertures in the upper part of the tube, the apertures being so disposed that a part of the slurry returns to the same vessel and a part of the slurry flows into a conduit which delivers it outwardly of the vessel. Such conduit may, if desired, lead'to the receiver of another similar vessel similarly equipped with slurry stirring and transporting means in accordance with the present invention.

In the accompanying drawings, which show a nonlimiting example of the apparatus in accordance with the invention:

FIG. 1 is a view in vertical longitudinal section through the apparatus of the invention;

FIG. 2 is a view partially in longitudinal vertical section and partially in elevation of a system having two storage vessels in accordance with the invention connected in series; and

FIG. 3 is a plan view of the system of FIG. 2.

In FIG. I there is fragmentarily shown a vessel or receiver 2, the receiver 2 being the right hand receiver of the two-receiver system shown in FIGS.2 and 3. The receiver 2 has the form more clearly shown in FIG. 2, that is, it has an upper elongated vertical circular cylindrical portion 19 and a lower, frusto-conical portion 20 mergingsmoothly therewith. The portion'of the apparatus shown inFIG. l is disposed in the upper portion of the vessel or receiver 2. A central tube I mounted at the top of receiver 2 has a flange 3 at the bottom thereof, such flange being connected to a similar flange 3a at the top ofa tube 4 which forms a prolongation of the tube 1 and extends centrally vertically downwardly to a point adjacent to but spaced from the bottom of the frusto-conical lower portion 20 of the receiver. Within tube 1 there is centrally mounted a turbine pump having helically disposed blades 5, such blades being mounted upon a central turbine pump shaft 6 which is supported in bearings 7 and 8 within an upper housing member which caps the upper end of the tube 1. At its lower end the turbine pump shaft is centrally guided by a bushing 9 which is mounted in the star or spider support 10 having slurry-conductingports therethrough. As shown, the support 10 is affixed as by being welded to the inner wall of the tube 1 at generally the level of the flange 3 thereon.

The pump shaft 6 is driven by an electric motor 11 through a plurality of V-belts 12 entrained over a V- belt pulley 13 on the pump shaft and a confronting pul ley on the shaft of the motor. The pump shaft 6 is driven in the direction indicated by the curved arrow in FIG. 1 so as to raise slurry which is admitted to the lower end of the tube 4 through windows D therein upwardly within the tube 4 thence through the ports in the support star of spider 9 and thence upwardly along the pump shaft within the tube 1. A plurality of vertically disposed radial guide blades 14 are affixed to the inner wall of the tube 1 so as to guide the thus-raised slurry upwardly within the tube and to prevent any substantial rotation of the column of slurry in the tube above the turbine pump. A part of the column of slurry thus raised by the pump is discharged through windows a in the upper end of the tube 1 so that it returns to the body of slurry within the vessel or receiver 2. The slurry is thus constantly stirred within the vessel.

Connected to the upper end of the tube 1 at one lateral position thereof there is a slurry-transporting conduit 16. One or more windows b through the wall of the tube 1 provide communication between the interior of the tube and the conduit 16. As shown in FIG. 1, window b is disposed at or about the same level as window a. The portion of the slurry which is not discharged through the window or windows a is thus discharged into the slurry-transporting conduit 16 through the window or windows b. In order to maintain a constant level of slurry in the receiver or vessel 2, there is provided a window 0 in the side wall of the conduit 16. A portion of the slurry which is initially introduced into the conduit 16 thus flows outwardly through the window c and returns to the receiver 2.

The apparatus of the invention includes means whereby the stirring of the slurry by the turbine pump 5 may be temporarily replaced by compressed air agitation thereof as during the failure of the current supply for motor 11 of the device or during necessary repairs to the parts of the vessel including the pump, motor, and pump-driving means. Thus there is provided a main, compressed-air pipe 18 from which there branches a pipe 17' which is led downwardly within the receiver 2 to the lower end of the pipe 4 adjacent the level of a window or windows d in the lower end of the pipe 4, as shown in FIG. 2. A selectively operable shutoff valve 17a is disposed in the pipe 17 as shown. When the shut-off valve 17a is opened, compressed air enters into the lower'end of the tube 4 thus elevating a column of slurry therein and causing the slurry to be continuously discharged through the window or windows a in the top of the tube 1. This prevents the settling of sediment in the bottom of the receiver or vessel 2, and the formation of encrustations on the inner surfaces and parts thereof.

In H652 and 3 there is shown a system which is composed of two similar receivers connected in series; here the above-described receiver 2 discharges slurry through the conduits 16 into a second, similar receiver through the slurry-discharge conduit 16 of the receiver 2. Parts of the receiver 15 which are similar to those of receiver 2 are designated by the same reference characters. Slurry is discharged from the second, left-hand receiver 15 through a conduit 16a either to a point of ultimate drying, packing, etc. or to a further receiver similar to the receivers 2 and 15.

The apparatus of the invention for stirring and transporting slurries has the following advantages:

The intense stirring of the slurry, which is not dependent upon the volume of the receiver or upon the volume of the slurry therein, causes the solid phase of the slurry, which is laid down on the conical bottom of the receiver, to be absorbed within the slurry and to be recirculated therewith. Encrustations, if any, which may temporarily form upon the side walls of the receiver are removed from the side walls of the receiver including those of the lower, frusto-conical portion thereof, upon the starting of the turbine pump. The apparatus of the invention provides for the good, vertical homogenization of the slurry. eliminates the foaming thereof, and eliminates the eventual chemical reactions which might otherwise take place between the components of the slurry and air, particularly the oxygen therein. The apparatus has a lower energy consumption, and is of simple,sturdy construction.

Although the invention is illustrated and described with reference to one preferred embodiment thereof, it is to be expressly understood that it is in no way limited to the disclosure of such a preferred embodiment, but is capable of numerous modifications within the scope of the appended claims.

What is claimed is:

1. Apparatus for stirring and transporting slurries comprising a vessel adapted to contain a slurry, a vertical tube disposed generally centrally of the vessel, a pump in the tube below the surface of the slurry for continuously raising a column of slurry upwardly in the tube, a first aperture through the sidewall of the tube above the pump for returning a portion of the column of slurry to the main body of slurry within the vessel outwardly of the tube, a second aperture through the sidewall above the pump at generally the same level as the first aperture, and a slurry discharge conduit receiving slurry from the second aperture.

2. Apparatus according to claim 1, comprising a second vessel connected to the end of the conduit outwardly of the first-recited vessel to receive slurry therefrom, said second vessel being similar to the first recited vessel.

3. Apparatus according to claim 2, wherein the two vessels are similarly disposed at substantially the same level, the outer end of the conduit being connected to the second vessel adjacent the upper end of the latter, the conduit having an opening through the sidewall thereof within the first vessel whereby to maintain substantially constant the level of slurries in the two vessels.

4. Apparatus according to claim 1, wherein the vessel is vertically elongated, and the tube reaches downwardly to adjacent the bottom of the vessel.

5. Apparatus according to claim 4, wherein the upper portion of the vessel is in the form of a vertically disposed circular cylinder, such circular cylinder forming a predominant part of the height of the vessel, and the lower portion of the vessel is of generally conical shape and is disposed coaxially of the upper portion of the vessel.

6. Apparatus according to claim 1, wherein the pump is a turbine pump having an impeller with helical blades mounted on a vertical pump shaft disposed centrally of thetube. 

1. Apparatus for stirring and transporting slurries comprising a vessel adapted to contain a slurry, a vertical tube disposed generally centrally of the vessel, a pump in the tube below the surface of the slurry for continuously raising a column of slurry upwardly in the tube, a first aperture through the sidewall of the tube above the pump for returning a portion of the column of slurry to the main body of slurry within the vessel outwardly of the tube, a second aperture through the sidewall above the pump at generally the same level as the first aperture, and a slurry discharge conduit receiving slurry from the second aperture.
 2. Apparatus according to claim 1, comprising a second vessel connected to the end of the conduit outwardly of the first-recited vessel to receive slurry therefrom, said second vessel being similar to the first recited vessel.
 3. Apparatus according to claim 2, wherein the two vessels are similarly disposed at substantially the same level, the outer end of the conduit being connected to the second vessel adjacent the upper end of the latter, the conduit having an opening through the sidewalL thereof within the first vessel whereby to maintain substantially constant the level of slurries in the two vessels.
 4. Apparatus according to claim 1, wherein the vessel is vertically elongated, and the tube reaches downwardly to adjacent the bottom of the vessel.
 5. Apparatus according to claim 4, wherein the upper portion of the vessel is in the form of a vertically disposed circular cylinder, such circular cylinder forming a predominant part of the height of the vessel, and the lower portion of the vessel is of generally conical shape and is disposed coaxially of the upper portion of the vessel.
 6. Apparatus according to claim 1, wherein the pump is a turbine pump having an impeller with helical blades mounted on a vertical pump shaft disposed centrally of the tube. 